Evacuated tube transport system with improved cooling for superconductive elements

ABSTRACT

A High Temperature Superconductor Maglev (HTSM) for Evacuated Tube Transport (ETT) with a magnetic levitation structure for ETT capsule vehicles traveling in an evacuated tube. At least one ETT capsule travels within an evacuated tube, an upper and a lower cryostat respectively mount at the top and bottom of said ETT capsule along the length thereof, at least a plurality of superconductor levitation force elements divided between said upper and lower cryostats. The levitation force being spread over the length of capsule, however substantially concentrated in a compact cross-sectional area. At least a pair of permanent magnetic elements mounted at the top and bottom of the evacuated tube to cooperate with the superconductor elements to levitate the capsule.

INCORPORATION BY REFERENCE

U.S. Pat. No. 5,950,543 issued 14 Sep. 1999 is incorporated herein byreference.

FIELD OF THE INVENTION

The present invention relates to rapid transit utilizing magneticallylevitated vehicle suspension, and particularly to energy efficientevacuated tube-transport systems.

BACKGROUND OF THE INVENTION

Automated Personal Rapid Transit (PRT), where automobile sized (orsmaller) vehicles independently operate on fixed rails. Most PRT systemdesigns use passive rails (analogous to freeways) that rely on steeringequipment in the vehicle to affect divergence to an alternative branch(analogous to an exit on a freeway).

The field of magnetically levitated vehicle suspension (maglev) includesa variety of 12technologies in the market. Most maglev vehiclesuspension technologies have been optimized for use in trains; severalrely upon active (mechanically movable) switch elements.

Train-type mechanical switch elements are limited in quickness,reliability and cost. Some mechanical switch elements wear over time,and reliability is dependent on the level of maintenance which can beextensive and costly. Importantly, mechanical switch elements take timeto engage, with some taking more than a second. Mechanical switchelements are inappropriate where the frequency of vehicle traffic isdesigned having a capacity of one vehicle per ten second interval orless, and especially those with intervals of less than one second. Alsomost mechanical switch elements wear considerably when operating everyfew minutes, instead of every few hours as with many train-basedsystems.

Electromagnetic Suspension (EMS) such as U.S. Pat. No. 8,234,981 B2August 2012 Zheng et al; and U.S. Pat. No. 8,171,859 B2 May 2012 Loseret al both of Germany (Transrapid) uses feedback control ofelectromagnets in the vehicle interacting with soft magnetic elements inthe to produce attractive levitation forces. EMS is able to maintainlevitation without forward movement; however it requires constant supplyof electric energy to produce the levitation force. EMS requiresconstant computer control to artificially stabilize inherently unstablemagnetic forces. EMS trains have some magnetic drag. The sum of the dragenergy and maglev operating energy is typically greater than the rollingresistance energy of the best steel wheel trains. Most EMS systems havebeen applied to train technology, and require the use of mechanicalswitch elements in the that seriously limit vehicle frequency.

Several maglev technologies use Neodymium permanent magnets (NdPM) inattraction, shear, or repulsion. NdPM can be made low drag if designedto minimize eddy current drag. Since NdPM maglev is inherently unstable,it must be stabilized by other forces such as rolling elements or EDSstabilization. Some examples are: U.S. Pat. No. 7,624,686 B2 December2009, U.S. Pat. No. 7,380,508 B2 June 2008, U.S. Pat. No. 7,314,008 B2January 2008, U.S. Pat. No. 7,484,462 February 2009, U.S. Pat. No.7,484,463 B2 February 2009, U.S. Pat. No. 7,243,604 B2 July 2007, andChinese Patent Publication No. CN1264660A titled “tube vacuum permanentmagnetic compensation type levitation train-elevated railway-stationsystem” all by Lingqun Li of Dalian China; and also U.S. 2006/0236890and U.S. Pat. No. 7,204,192 B2 April 2007 to Lamb et al(MagnaForce/Levex) of the US that uses NdPM in vehicle and whereguidance force must stabilized with contacting rollers that are subjectto speed limitations, wear and sudden failure. U.S. Pat. No. 5,218,257June 1993 Tozoni of MD USA, and U.S. Pat. No. 5,225,728 July 1993 Oshimaof Japan both claim stable PM maglev, however the configurationsindicated have not been demonstrated to work even though now expired andin the public domain.

U.S. Pat. No. 7,757,609, issued July 2010, U.S. Pat. No. 6,684,794,issued February 2004, U.S. Pat. No. 6,374,746, issued April 2002 all toFisk et al. uses NdPM in both the vehicle and to supply repulsive liftforce, and EMS control to provide “steering” forces and stability, andthe capability of full speed interchanges with converge and divergefrequency limited only by the vehicle length and speed and constantelectronic measurement and control. Magtube relies on constant computercontrol for operation, as well as constant electrical supply to energizethe electromagnetic coils. However, a constant electrical supply resultsin losses in electrical efficiency.

U.S. Pat. No. 7,448,327 B2 November 2008 Thornton et al. Assigned toMagnemotion (M3) uses NdPM to provide about half of the attractivelevitation force, this reduces the energy requirements of EMS, but stillrelies on constant computer control and electric energy supply. M3 canlevitate only up to ten times the magnet weight; and requires mechanicalswitching that limits vehicle frequency.

There is risk of loss of electric energy supply or computing power orstability augmentation with the above maglev systems; such failure wouldresult in the vehicle contacting the and possible damage. Most of thesystems have crash pads made of heat resistant friction material toabsorb the kinetic energy of the vehicle in the event of a crash.

Electrodynamic Suspension (EDS) maglev can be configured so thatmechanical switches are not required to inject vehicles into the flow oftraffic on the. EDS maglev systems can be designed to produce stablelevitation without constant electric supply or constant computercontrol. EDS systems require forward motion of the vehicle to producelevitation. EDS maglev uses magnetic fields in the vehicle to induceelectric currents in the. The currents in the produce an opposingmagnetic field that lifts the weight of the vehicle when velocity issufficient. An example of EDS is the Japanese National Railway maglevtrain that currently holds the world record maglev speed. The JapaneseEDS uses superconducting magnets in the vehicle interacting with analuminum plate in the. The superconducting magnets must be cooled toliquid helium temperature so it is very expensive to operate. Themagnetic drag of EDS is very high at low speed, reaching a maximum at“liftoff”. The drag only diminishes with increasing speed, so at low tomedium speeds the drag can result in less-than-optimal energyefficiency.

Another EDS prototype named Inductack was invented by Dr. Post ofLawrence Livermore National Lab. (U.S. Pat. No. 6,664,880 December 2003,and U.S. Pat. No. 6,633,217 October 2003). Inductrack uses NdPM Halbacharrays in the vehicle interacting with copper wire coils in the.Inductrack prototypes have demonstrated a potential lift to drag ratio(L/D) of about 400:1 at 200 mph, this about five times the rollingresistance of a steel wheel high speed train at the same speed. Asimilar EDS-PM arrangement is disclosed in U.S. Pat. No. 7,950,333 B2 toCrawford et al (Disney) with no provisions for interchange or switching.

US 2008/0148988 A1 and U.S. Pat. No. 8,171,858 May 2012 and U.S. Pat.No. 7,562,628 all by Wamble et al (Skytran) uses NdPM elements andelectric coils in a configuration allowing non-mechanical switching,however the drag force is high at low speeds, and it requires provisionfor touchdown at low speed or stops. The Skytran switch design has speedlimitations imposed by safety and structural limitations of theconverge/diverge angle (or risk of diverge failure). Further limitationsof Skytran are levitation force is reduced in the zone of thediverge/converge segment necessitating double the amount of magneticmaterial (and/or passive lift coils) in the and/or vehicle. A furtherlimitation is that in the diverge zone of the switch, active electricmagnetic force (with position control feedback) is required to counterthe unbalanced passive repulsion force on the continuation path side ifthe vehicle is desired to continue on; OR to supply activeelectromagnetic divergence force and electronic sensing and control fora diverge to occur. If electronic sensing and force control is not used,rollers or skids are required to prevent unwanted contact with magneticcomponents. Very high reserve forces in the electromagnetic elements ina diverge zone are required to counter variable side wind forces actingon the vehicle. Yet another limitation is that the steering forces donot act on the center of gravity of the vehicle, and swinging of thevehicle is likely to occur from lateral switching forces and/orpassenger movements or wind force. Another problem is that propulsiveforces act far from the center of gravity of the vehicle potentiallycausing pitching excitations that require clamping force generators toovercome.

U.S. Pat. No. 5,631,617 May 1997 to Morishita of Japan, and U.S. Pat.No. 7,197,987 B2 April 2007 Falter et al. of Germany disclose HighTemperature Superconductor Maglev (HTSM) that uses NdPM in the thatinteracts in attraction and/or repulsion with diamagnetic YBCO(Yttrium-Barium-Copper-Oxide) superconductive bulk crystals in thevehicle. HTSM levitation is capable of producing attractive force,repulsive force, and shear force between the superconductive (SC)elements and the Permanent magnet (PM) elements in the. HTSM levitationforce and restoring force is dependent on the magnetic force gradient.For HTSM to function the SC elements (for instance YBCO) must bemaintained at cryogenic temperatures (below 91 Kelvin in the case ofYBCO) to enter the superconductive state. HTSM was first demonstrated tocarry passengers by the inventor WANG Jaisu a professor of South WestJaiotoung (transportation) University (SWJTU) in Chengdu China 31 Dec.1999. Prof. Wang has been granted several patents in China that relateto HTSM. Wang's HTSM is very stable without computer control or energysupply. The HTSM prototype exhibited very stiff suspension in thevertical direction, and had a small degree of freedom (about 5 mm) inthe lateral direction with only a few Newtons of force, and thenencountered very stiff resistance requiring over 5000 N displacinganother 5 mm in the lateral direction. The prototype HTSM by Wang wasnot optimized to reduce cost or magnetic drag force. Furthermore, theHTSM prototype at SWJTU has a problem (especially during times of humidair conditions) of ice forming on the cold surface of the vehicleimmediately above the suspension gap. HTSM configured to operate in theopen environment is also subject to stray ferromagnetic material beingattracted to attach to the permanent magnets in the and pose a risk topassing vehicles. NdPM is subject to corrosion problems in the open air,and NdPM is usually plaited with corrosion resistant metals to helpprolong service life of NdPM elements exposed to the atmosphere.Metallic plaiting can contribute to increased drag force.

U.S. Pat. No. 6,418,857 July 2002 Okano et al. of Japan, makes use ofvacuum to mitigate the frosting and magnetic attraction and corrosionproblems of HTSM, however another problem remains: the use of liquidnitrogen (LN2) as a heat sink to maintain temperatures below 91 Kelvinnecessary for HTSM function. The use of LN2 for ETT-HTSM is not optimaldue to the large volume change of gas phase compared to liquid phase.Use of LN2 for ETT-HTSM would necessitate either onboard compression andstorage (heavy, expensive, and energy intensive); or release of the N2gas to the evacuated environment in the tubes (loading the vacuum pumpsand dramatically increasing energy use). The HTSM prototype by Wang usedabout 35 liters of LN2 during the maximum levitation time of 7 hours.The LN2 boils away and is vented to the atmosphere. While not a poison,N2 gas can displace oxygen in enclosed spaces and result inasphyxiation. Okano provides no way to interchange vehicles.

Experience with rotary HTSM bearings has shown that the L/D can be ashigh as a hundred million. The HTSM prototype in Chengdu required alarge quantity of expensive neodymium permanent magnets (NdPM), and useda configuration of NdPM that produced significant drag force resultingin a L/D of about 1000:1.

HTSM configurations that use High energy Neodymium PM material (NdPM) inHalbach arrays to focus the magnetic force and thereby reduce thequantity of magnetic material necessary to generate a levitation force;and do not require electrically conductive soft magnetic elements thatexhibit increased eddy current drag.

SUMMARY OF THE INVENTION

The present invention seeks ultimately minimize energy consumptionrequired for transportation systems. The present invention overcomes thelimitations of the prior art, while exhibiting many useful advantages aswill become evident in this disclosure.

The present invention focuses on the field of automated transportationof goods and passengers in magnetically levitated capsules independentlyoperating in evacuated tubes. The field has not yet been widelycommercialized; however it has the potential to dramatically reducetransportation construction and operating costs if properly optimizedfor maximum transportation value. In particular, significant costsavings are realized through transportation energy efficiency. Othercost savings are realized by lowering the capital costs forconstruction.

Various benefits of the High Temperature Superconductor Maglev (HTSM)for Evacuated Tube Transport (ETT) with a magnetic levitation structurefor ETT capsule vehicles traveling in an evacuated tube in accordancewith the present invention are set forth below:

The capsules are designed to be light weight structure with a very lowdrag force thereon, which minimizes energy consumption required fortransportation. Further, operation is not dependent on constant electricsupply or constant computer control, which further reduces energyconsumption.

A further energy-saving aspect of the present invention is to usesolid-liquid phase change instead of liquid-gas phase change in order tomaintain cryogenic temperatures necessary for superconductivity.

Construction costs are minimized by optimization of the levitation gap,and reduction of cross-sectional areas.

Still another benefit of the present invention is to dispense with anylimitation on the design speed during converge or diverge operationduring an interchange of tubes.

A further benefit of the present invention is to avoid the necessity ofany mechanical or electrical switch elements to be used in the tube,which reduces the cost of construction.

A performance benefit of the present invention is to provideultra-stability to capsule vehicles in roll, pitch and yaw. Anotherperformance benefit of the present invention is to ensure that there isno reduction of levitation force during a divergence or convergence.

A safety benefit of the present invention is to use a heat sink materialthat does not result in emissions of gas to the capsule or evacuatedenvironment.

In accordance with the present invention, there is provided a HighTemperature Superconductor Maglev (HTSM) for Evacuated Tube Transport(ETT) with a magnetic levitation structure for ETT capsule vehiclestraveling in an evacuated tube. The magnetic levitation structurecomprises:

-   (a) at least one evacuated tube supported on support structures at    intervals;-   (b) at least one ETT capsule traveling within the evacuated tube;-   (c) an upper and a lower cryostat respectively mounted at the top    and bottom of the ETT capsule along the length thereof;-   (d) at least a plurality of superconductor levitation force elements    divided between the upper and lower cryostats, the levitation force    being spread over the length of capsule, however substantially    concentrated in a compact cross-sectional area;-   (e) at least a pair of permanent magnetic elements mounted at the    top and bottom of the evacuated tube to stably levitate the capsule    within the;-   (f) at least a pair of capsule based switchable diverge force    elements; and-   (g) at least a pair of tube based diverge force elements.

Typically, the cryostat is mounted internally on the capsule to passthrough a cylindrical airlock with minimal time and energy.

Typically, the cryostat is mounted externally on the capsule to preventany harm to occupants by leakage of material and to make more spaceavailable in the capsule.

The cryostat is made of an electrically non-conductive material andconfigured in a cylindrical shape to house the superconductor elementsfor use in linear induction motor/generator for capsuleacceleration/deceleration, the material providing sufficient strengthand stiffness to resist internal pressure, thermal stresses andlevitation forces.

Typically, the cryostat is mounted on the ETT capsule by means ofinsular mounting elements and the levitation force imparted tosemiconductor element is transferred via a force transfer structure tocryostat and from cryostat to ETT capsule without providing a heat pathfrom cryostat to capsule.

Typically, the cryostat is mounted on the surface of the ETT capsule bymeans of removable mounting element, configured as quickly removablemagnetic force attachment means for ensuring ultra-insulated andultra-dry conditions of the evacuated environment and to allow transferof the capsules through the airlock by removing the cryostat from theinbound capsules while in the evacuated environment and before thecapsule enters the airlock. This offers energy savings by allowing thecapsule to displace virtually all of the air in the airlock; thereforeless electrical energy is required for vacuum pumps on each airlockcycle.

The cryostat contains superconductor elements made ofYttrium-Barium-Copper-Oxide (YBCO) crystals or vapor deposited YBCOfilms, or any other superconductive materials with a high criticalcurrent density known to those versed in the arts.

The sealed cryostat contains a cryogenic solid-liquid (SL) phase changematerial whereby the superconductor elements are cooled by means of thecyrogenic heat-sink substance or a coolant having a solid-liquid phasechange (melting cycle).

The cryostat interfaces with automated cryostat handling and re-freezeequipment that replaces any re-frozen cryostat onto outbound ETTcapsules; removable cryostats allows the use of an airlock only slightlylarger diameter than the capsule in order to minimize airlock cycle timedue to nearly complete air displacement by the capsule in the airlockchamber.

The solid-liquid phase change material is placed in the cryostat withexpansion mitigation means for always keeping the solid-liquid phasechange material in contact with the superconductor elements for allowingexpansion and contraction of the liquid and/or solid material duringnormal operation and handling and during the necessary thermal cyclingof a plurality of melting and re-freezing cycles.

The expansion mitigation means is configured as an empty space or aflexible membrane separating a portion of the cryostat or a compressiblebillow type of structure for allowing changes in volume without applyingdamaging pressures to the cryostat.

Alternatively, the cryostat is provided with reaction members as movingpart of linear electric motor (LEM)/linear electric generator (LEG)having coil elements mounted on tube.

A plurality of permanent magnetic elements are secured to the tube bypermanent magnet mounts, which are non-conductive to allow precisionalignment of the permanent magnetic elements with respect to the tubestructure to compensate for any manufacturing irregularities of the tubesurface or diameter while maintaining the permanent magnetic elements inproper alignment to produce uniform levitation force on the capsulecomponents. The magnet mounts are secured to the wall of the tube by anyknown means including but not limited to: adhesives, embedded elements,or threaded or riveted fasteners.

In one embodiment, the permanent magnetic elements are divided intosmaller units in the linear direction with slight space between theelements. A spacer is interposed between each of the permanent magnetelements. The spacers are made from a material that is both elastic anddielectric. Spacer elasticity compensates for linear movements caused bythermal variations and/or minor geological forces.

The dielectric aspect of the spacers reduces magnetic drag forces andimproves lightning protection by reducing electrical conductivity in thelinear direction along the tube so that any electromagnetic pulse with ahigh orthogonal potential will not cause harmful electric currents inthe linear direction. Another benefit of the dielectric spacers is thatharmful magnetic forces that could damage the magnets, holders, or tubestructure are inhibited by the dielectric material limiting electricalconductivity in the linear direction along the tube.

The cryogenic solid/liquid phase change material is a heat-sink materialselected from the group comprising of propane, propane mixtures, orother materials that melt at any temperature below the transitiontemperature of the superconductor material. Propane and most otherflammable materials require oxygen for combustion. In the evacuatedenvironment there is virtually no oxygen. In the unlikely event of aleak of a normally combustible material from a damaged cryostat, thereis reduced risk of fire compared to vehicles operating in the with openair with large quantities of fuel.

In one embodiment, a portion, up to half, of the superconductorlevitation force material is replaced with permanent magnet materialthat is oriented in attraction in the upper cryostat and is oriented inrepulsion in the lower cryostat such that sufficient stability ismaintained at reduced cost.

The insular mounting element is made of thermally insulting structuralmaterial selected from the group consisting of syntactic foam, aerogel,polycarbonate foam, or other suitable insulating material.

In accordance with the present invention, there is also provided amethod of interchange of High Speed High Frequency Maglev, the methodcomprising the steps of: automation of convergence and divergenceoperation between capsule traffic flows in intersecting or bifurcatingbranches thereof by predetermining the switching operation either beforethe journey or during an emergency situation in route without theoccupant being able to directly control the active components in thecapsule vehicle; energizing the switchable diverge force elements bypermanent magnets for creating bi-stable positions to allow the capsulevehicle to either continue on tube or to diverge; or a DPDT bi-stableelectric switch that selectively energizes the electromagnet switch toselect the capsule vehicle to either continue on tube or to diverge;preventing the reorientation of the switchable diverge force elements bymeans of an interrupter while the capsule vehicle is approaching or isin the diverge zone; fixing predetermined speed of the capsule vehiclein the interchange zone; predetermining the divergence by activation ofbi-stable magnetic diverging force elements in the capsule vehicleduring the divergence of the tube s, the changes in divergence forceonly activated prior to entering the divergence zone and disabling themodification of divergence forces while capsule diverges; balancing thedivergence forces through centre of gravity and through center of lifton receiving a request from the occupant of an ETT capsule for adivergence, wherein the occupant is not able to directly control thedivergence force; and limiting the frequency only by predeterminedspeed, predetermined capsule spacing, converge timing and speed matchingduring the convergence of the tubes.

Typically, the control system flags the ETT capsule for removal fromservice and repair at the next access portal, if the switch isimproperly oriented by failure, a certain lateral jerk and light impactforce is produced by sudden lateral movement across the width of thepermanent magnet, which is sensed by position sensors and/oraccelerometers in the capsule to indicate the likelihood of a componentfailure in the switch elements in the capsule.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of a typical High TemperatureSuperconductor Maglev (HTSM) for Evacuated Tube Transport (ETT).

FIG. 2 a is a cross-sectional view of HTSM shown in FIG. 1 with one ofthe tubes accommodating an ETT capsule.

FIG. 2 b is a HTSM cryostat externally mounted on the capsule of FIG. 2a.

FIG. 3 a is a cross-sectional view of HTSM shown in FIG. 1 with one ofthe tubes accommodating an ETT capsule with internally mounted cryostatconfiguration.

FIG. 3 b is a cross-sectional view of a cryostat mounted in FIG. 3 a.

FIG. 4 a is a sectional top view showing tubes at an interchange withassociated lateral displacement force diagrams, with the dotted lineslabeled “NSF” to indicate normal steering force level, and “ESF” forexceptional or emergency steering force level.

FIG. 4 b is a cross sectional view of a capsule moving in the tube atthe interchange of FIG. 4 a with the dotted line showing lateralmovement caused by the tube based lateral force elements.

FIG. 5 is a cutaway view of a curve section of double tube with acapsule in the upper tube.

FIGS. 6 a, 6 b and 6 c show typical sections of the double tube ETT inthree different sections, i.e. in a highway median, in an optional lowprofile configuration and in an optional double pair to miss utility.

FIG. 7 shows the automated loading and unloading of cryostats fromcapsules docked at an interchange.

DETAILED DESCRIPTION

FIG. 1 shows a pair of tubes 200 stretching across a landscape. Thetubes mount on concrete pillars 90 and are shown above ground.Above-ground construction reduces costs and eases maintenance andinspections. It can be appreciated that below ground and underwatermounting of the tubes 200 is also viable in accordance with the presentinvention.

The pair of tubes 200 enables simultaneous transport of capsules 300 inopposite directions.

FIG. 2 a shows a cross-section of a capsule 300. The capsule 300levitates in the tube 200. The tube includes diverge force elements 194.The capsule 300 includes switchable diverge force elements 190.

The tube 200 has a circular cross-section and sized having a diameter toaccommodate two passengers seated shoulder-to-shoulder. A superconductor(SC) element 100 mounts in opposing arrangement on the external surfaceof the capsule 300.

FIG. 2 b shows a cross-section of the superconductor (SC) element 100,which includes permanent magnets 105, a mounting element 106, alevitation gap 108 and a cryostat 110. The superconductor element 100also includes coolant 120, insular mounting elements 140 and removablemounting elements 150.

FIG. 3 a shows a cross-section of the tube 200 holding the permanentmagnet element 106 within the evacuated tube way. The cryostat 110mounts within the interior of the capsule 300.

FIG. 3 b shows an enlarged view of the tube 200, the permanent magnetelement 106, the capsule 300 and the cryostat 110 mounted within thecapsule 300. The cryostat 110 houses superconductor elements 100. Thecryostat 110 also houses coolant 120 and has expansion mitigation 170 toenable the coolant 122 expand when changing phase. The cryostat 110 alsoincludes insular mounting elements 140 that insulate the cryostat 110from the ambient environment within the capsule 300.

FIG. 4 a shows the tube 200 at an interchange 202. In the interchange202 the tube 200 diverges into two branches. The tube based divergentforce elements 194 (shown with dotted lines) provide magnetic force toenable the tube based divergent force elements 194 to cooperate with thecapsule-based switchable diverge force elements 192 steer the capsuleinto one of the divergent branches of the tube 200. The divergentbranches of the tube 200 each house permanent magnets 105 to enablecontinued suspension of a capsule 300 moving within either branch of thetube 200.

FIG. 4 b shows movement of the capsule 300 laterally during movementthrough the interchange 202 region of the tube 200. Lateral movement ofthe capsule 300 as shown by the dotted lines steers the capsule 302 oneof the divergent regions of the tube 200. Such lateral movement ispreprogrammed into the system so there is no need for occupants 2042steer the capsule 300

FIG. 5 shows an end view of two tubes 200 and vertical alignment witheach other in accordance with FIG. 1. The tubes 200 curve. Accordinglythe insular mounting elements 140 are aligned off-center on the topportion and the bottom portion of each tube 200. This holds eachcryostat 110 in off-center alignment with the top portion in the bottomportion of each tube 200. Off-center alignment of the cryostat's causeany capsule moving through the tube 200 to rotate so as not to causeoccupants or cargo in the capsule 300 to shift laterally during movementthrough a curve.

FIGS. 6 a, 6 b and 6 c show various configurations of the tubes mountedon pillars 90. In particular FIG. 6 a shows a configuration of the tubesin a highway median and the tubes 200 are in a typical verticallyaligned configuration. FIG. 6 b shows the tubes 200 on an extendedpillar 90 to avoid utility lines, or other obstacle positioned on theground. FIG. 6 c shows a low profile configuration having the tubes 200in lateral alignment with each other to avoid an obstacle such as anoverpass, or to enable the system to fit within a tunnel.

FIG. 7 shows two tubes 200 positioned in vertical alignment within theinterchange region 202. In this embodiment the interchange region 202 isa specialized interchange that allows for docking, loading and unloadingcargo from each capsule 300. The interchange region 202 includes aninterchange structure 208 for pressurization and depressurization of theinterchange region 202. A transfer mechanism releases and re-attachesfully cooled cryostat 110 on to each capsule 300 while each capsule 300remains stationary in the interchange region 202. Numerous cryostats 110are systematically cooled and attached to and detached from capsules 300and an evacuated environment in the interchange region 202 by means ofan automated refreeze equipment 160. Each cryostat 110 attaches to thecapsule 300 with a removable mounting element 150 attached at a topportion and bottom portion of the capsule 300. The interchange structure208 enables pressurization and the depressurization of the interchangeregion 202.

Details and Operation

ETT-HTSM lifting force is generated by superconductor elements 100attached to the capsule. Many superconductor materials are known tothose versed in the arts, presently the best superconductor material forHTSM is bulk Yttrium Barium Copper Oxide (YBCO) crystals or vapordeposited YBCO films. YBCO requires cryogenic cooling to temperaturesbelow 91° K to become superconductive and produce the requiredlevitation force when interacting with permanent magnet elements 105that mount in the tube 200.

The cryostat 110 is a container designed to stay at the low temperaturerequired to maintain the superconductive state of the superconductormaterial. It is anticipated that superconductor materials could bedeveloped in the future that will not require cryogenic temperatures,and will be able to enter the superconductive state at ambient roomtemperature. To omit the need for a heat-sink and/or cryostat does notdiminish the other novel objects and advantages of the present inventionas will become apparent.

The cryostat 110 makes use of a solid-liquid (SL) phase change (meltingcycle) coolant 113 for HTSM instead of a liquid-gas (LG) phase change(boiling cycle). To reduce the material use, thickness, and heat gain,the cryostat 110 is preferably cylindrical in shape and of a uniformdiameter along the full length of the capsule 300 to be levitated. Thepreferred material is non-conductive to electrical energy in order tokeep eddy current drag low, and able to provide sufficient strength andstiffness to resist internal pressure, thermal stresses, and levitationforces.

There are several heat-sink substances 113 that freeze below the 91° Ktransition temperature of YBCO to enter the superconductive state aswill be apparent to those versed in the art. For instance, propane(C₃H₈) melts at 85.5° K; this is between the 77° K, the boiling point ofLN2 and the 91° K the critical temperature (T_(c)) of YBCO. Liquids thatfreeze at lower temperatures have the advantage of reducing the amountof YBCO to produce a desired levitation force, but take more energy (orLN2) to refreeze, and may have a critical temperature below roomtemperature (resulting in risk of burst or thick heavy containment). Asknown to those versed in the arts, the freezing point of propane (andother appropriate liquids) can be modified by adding solutes (much asthe freezing point of water is reduced by adding salt or ethyleneglycol).

The cryostat 110 can be mounted externally (FIG. 2) or internally (FIG.3) on the capsule 300. Internal mounting has the advantage of being ableto pass through a cylindrical airlock with minimal time and energy;however the quantity of superconductor material 100 must be greater toprovide a desired levitation force and clearance due to the addedthickness of the pressure hull, and thermal insulation material.

In a preferred embodiment the cryostat 110 removeably mounts external tothe capsule 300, i.e. on an external surface of the capsule 300.External mounting is preferred for several reasons: any leaking materialwill not endanger the occupants, the insulation qualities of theevacuated environment are fully exploited to reduce the thermal heatgain thereby reducing the quantity of SL phase change material 120, moreroom is available in the capsule 300, less superconductor material 100is required to produce a given levitation gap, the cryostat can beeasily removed while in the vacuum environment to re-freeze limitingthermal cycling wear and tear.

Thermally Isolated Structural Mount:

The cryostat 110 for ETT-HTSM is structurally mounted to the capsule 300such that the levitation force imparted to the superconductor elements100 are transferred to the cryostat via a force transfer structure 130,such as but not limited to adhesive or mechanical means, and from thecryostat to the capsule. The mounting elements 140 in contact with thecryostat are thermally isolated from the capsule by using a structuralmaterial that is resistant to thermal energy flow such as (but notlimited to): aerogels or thermoplastic foams, and/or vacuum insulationas known to those in the arts. In this way, the superconductor material(such as YBCO) is secured at the proper location in the cryostat withmechanical and/or adhesive means to provide a load path for thelevitation force from the superconductor material to the cryostat 110,from the cryostat 110 to the insulating mounting elements 140, andultimately to the capsule 300, but without providing a heat path fromthe cryostat 110 to the capsule 300.

Magnetic force attachments 150 removeably attach the cryostats 110 tothe capsule 300. This enables rapid removal and replacement of thecryostats 110. This is advantageous because the magnetic forceattachments 150 enable the cryostats 110 to be removed and replaced inthe evacuated environment. The evacuated environment is ultra-insulatedand ultra-dry to minimize heat transfer to the cryostats 110 so it ispreferable that the cryostats 110 are removed and replaced prior to, orafter, entry of the capsule into the airlock. This embodiment enablesthe capsules to be transferred through the airlock at standardtemperature and pressure, while quickly enabling removal and replacementof the cryostats 110 with the magnetic force attachments 150 in theevacuated environment of the tube.

Automated Re-Freeze or Replacement Equipment 160:

Removable mounting allows automated means to remove any cryostat frominbound capsules, placed it in contact with cryogenic heat transferfluids (such as LN2) that re-freeze the SL heat-sink material. And thenthe automated equipment 160 functions to replace any re-frozen, oralready frozen reserve cryostat 110 onto outbound capsules 300. Thisminimizes airlock cycle time due to greater air displacement by thecapsule 300 in the airlock chamber. It also results in fewer failurepoints or stress risers in the capsule pressure hull.

It can be appreciated that the automated equipment 160 have thecapability to store a plurality of cryostats 110 in fully operationalcondition, i.e. fully frozen, to enable faster throughput of capsules300 through any interchange in systems employing tubes 200.

Use of SL phase change produces only a small volume change compared to aLG phase change. The SL heat sink material 120, preferably propane isplaced in a sealed cryostat 110 with an empty or compressible volume 170as required to allow for expansion and contraction of the liquid (and/orsolid) material during normal operation and handling, and during thenecessary thermal cycling of many melting and re-freezing cycles. Theexpansion mitigation means 170 can be empty space in the cryostat 110, aflexible membrane separating a portion of the cryostat 110, or a billowstype of structure to allow for changes in volume without applyingdamaging pressures to the cryostat cylinder. One function of theexpansion mitigation structures is to keep solid or liquid phaseheat-sink in contact with the superconductor material 100 at all times.

Linear Motor/Generator:

An ETT-HTSM cryostat 110 can be provided with cooling capacity. Afreezer element integral with or operably connected with the cryostat110 regulates the temperature of the cryostat 100 to optimize operationbetween interchanges. Accordingly the freezer element is only operatedwhen necessary to minimize energy consumption of any system utilizingtubes 200. One way of powering the freezer element to add additionalcapacity and cool superconductive elements 100 used for reaction members180 that move, i.e. rotate or translate with respect to the tube 200axis. The reaction members 180 operably connect with a Linear ElectricMotor (LEM) or Linear Electric Generator (LEG) coils 182 mounted on thetube 200.

Embodiment with Permanent Magnet Elements 105 for HTS Reduction:

The stabilizing effect made available by any superconductor element 100depends on the relative position in relation to the center of gravity ofthe capsule. Superconductor elements 100 mounted close to the capsuleends contribute a greater pitch and yaw restoring moment to the capsulethan SC elements 100 situated close to the center of the capsule. Aportion of the superconductor elements can be replaced with permanentmagnet material 105 such as NdPM to reduce the cost with little loss tothe stability while maintaining the required levitation force andsuspension levitation gap.

Maglev Configuration for ET3:

The levitation force of HTSM is a function of the amount of forceapplied by the superconductor 100 (for instance YBCO), and permanentmagnet 105 (for instance NdPM) that are configured to magneticallyinteract to levitate the capsule. To minimize cost, it is desirable toreduce the cross-sectional area of the permanent magnet material 105 inthe. A fixed quantity of superconductor material 100 is required toproduce a given levitation force and levitation gap 108. To minimize thecost, the present invention spreads the required quantity ofsuperconductor elements 100 out over the entire length of the capsule,resulting in a narrow strip of SC material 100. To have high rollstability, the superconductor material 100 is divided between theextreme top and bottom extremities of the capsule cross-section. Thisdistribution results in high lateral, roll, pitch, and yaw stability;and also a small sectional area of permanent magnet material 105 in the.

The permanent magnet material 105 (for example NdPM arranged in aHalbach array) is secured to the tube with structural permanent magnetmounts 106 that are non-conductive, and allow precision alignmentadjustment of the permanent magnet elements 105 in relation to the tubestructure to compensate for irregularities of the tube 200 surface ordiameter; while maintaining the permanent magnet elements 105 in theproper alignment to produce uniform levitation force on the capsulecomponents.

Intentional periodic discontinuities across the linear dimension of thepermanent magnet mounts 106 allow for normal thermal expansion andcontraction of the tube without introducing misalignment, high stress,or loss of integrity. The permanent magnet material 105 is preferablydivided into small units in the linear direction with slight spacebetween the elements enforced by a spacer 107 made from an elastic anddielectric material that is able to continuously compensate for linearmovements caused by thermal variations and/or minor geological forces.

The elastic material 107 is dielectric to reduce magnetic drag forces,and also mitigate potential damage from electromagnetic pulse (such ascaused by lightning strike). The dielectric permanent magnet coatingmaterial 107 (and/or permanent magnet mounting structure 106) is ideallymade of low friction material (such that the permanent magnet elements105 are free to slide in the linear direction so linear gap variationsbetween individual permanent magnet elements 105 resulting from linearthermal deflections are uniform, yet accommodated at any expansionjoints between tube sections as required by local conditions.

Levitation Height:

For low superconductor 100 and permanent magnet 105 material cost, thelevitation gap 108 must be minimized; however for low construction costof the reasonable tolerances are necessary indicating need for a largelevitation gap 108. The optimal levitation gap 108 results in the lowesttotal system cost. ETT-HTSM allows for reduced gap 108 by: use ofsupport structures that are ultra-stiff in the vertical, lateral, andtorsional directions, use of precision alignment adjustment structures(such as opposing wedges, or locking threads, active alignment measuringand control that maintains the accurate alignment of the permanentmagnet elements 105 even if the earth should move (refer to relatedapplication disclosing active alignment),

Crash protection may be built into the linear motor components 182and/or the cryostat 110 as is known to those in the arts. Thesecomponents sustain damage first to protect the integrity of the pressurehull in the unlikely event of a crash.

Magnetic Drag Force Reduction:

Features of ETT-HTSM that contribute to low magnetic drag are: a)avoidance of the use of electrically conductive elements in the capsule.

Sources of HTSM Drag:

Plating of permanent magnet 105 or superconductor 100 elements;resistive Conductivity of permanent magnet elements 105 orsuperconductor elements 100; Iron or soft steel pole pieces;electrically conductive (metallic or carbon fiber) mounting materials;Magnetic field flux gradient variations in the linear direction causedby: magnet strength, magnet position variations, and magnet size orshape variations, and/or electrical conductivity variations. In additionstray magnetic fields “trapped” or “pinned” in the superconductorelements 100 (such as from earth fields or other fields that may varyaccording to capsule directional orientation.

Magnetic hysteresis losses from relative vertical and horizontal motionof the superconductor elements 100 in relation to the permanent magnetelements 105 such as caused by: vibrations of or capsule; variablevertical and horizontal forces (such as induced by load movements orcurvilinear accelerations, or externally induced movements of earth orwind acting on; and or those internal to the system such as micromisalignment of permanent magnet material 105 in relation to the, and/ormacro misalignment of the; and finally losses induced by deflections ofthe earth, alignment mounts, and/or permanent magnet material 105, andor periodic deflections in the structural elements in the capsule tosuperconductor elements 100.

Minimization of Drag Forces:

Eddy currents in the permanent magnet 105 are minimized by using bondedmaterials that are not electrically conductive (but this results in lessmagnetic force and more material), or by using smaller physicaldimensions in the plan view to minimize eddy current area and force.

Superconductor 100 and permanent magnet 105 elements are preferablycoated with a non-conductive material.

In another embodiment, the superconductor 100 and permanent magnet 105are coated with metallic or electrically conductive materials tomaximize reflection of heat energy. However, the conductive elementsshould are oriented to minimize eddy currents, and maximize the distancefrom magnetic fields (generated by permanent magnet 105 orsuperconductor 110 elements in the 200 or capsule 300) that moverelative to the conductive element.

Preferably the superconductor 100 and the permanent magnet 105 arecoated with reflective materials such as metalized dielectric films tominimize radioactive thermal heat gain to the cryostat 110. This isimportant because the temperature difference between portions of thecapsule and portions of the cryostat 110 creates the potential forsignificant heat transfer via radiation.

When such metalized films are used for thermal radiation mitigation, asmall portion or kerf of the reflective material can be burned off bylaser (or photo etched, or masked) in a micro grid pattern to limit theformation of large eddy currents in the conductive layer but stillreflect most thermal radiation energy.

When cooling superconductor elements 100 to the point ofsuperconductivity in the presence of a magnetic field ensure that thefield shape and distribution is identical to the magnetic flux field inthe, and that the earth's field is either excluded by use of a Faradaycage shield, and/or aligned to coincide with the direction of theEarth's field for the major alignment especially those in high speedsections.

Use non-conductive permanent magnet material 105 for as much of the loadcarrying as possible; using just enough superconductor material 100 toachieve sufficient stability in worst case conditions. Electricallyinsulate any conductive permanent magnet element 105 from each otherwith dielectric materials 107 that also may function elastomerically aslinear thermal stress mitigation (note that this also mitigates EMPrisks).

By use of accurate tube 200 and permanent magnet 105 alignment tominimize acceleration and levitation force variations; Use accurate andconsistent permanent magnet 105: size, placement, spacing, strength, andfield shape consistency. Tube 200 and capsule 300 utilize structuralcomponents that are very stiff in the vertical and lateral directions tominimize physical deflections. Use light weight capsules 300 to minimizetube 200 deflections and to protect capsule 300 and tube 200 from (orotherwise mitigate) variable loads such as but not limited to: side-windloads, aerodynamic oscillations, earth movements, and payload movements.

Automation of convergence and divergence between traffic flows inintersecting or bifurcating branches at any predetermined fixed designspeed at all times in interchange zone,

-   -   Convergence:    -   frequency limited only by design speed    -   per-determined capsule spacing, and converge timing and speed        matching    -   Divergence:    -   predetermined by activation of bi-stable magnetic diverging        force elements in the vehicle    -   divergence force changes can only be activated prior to entering        divergence zone    -   physically impossible for divergence forces to be modified while        capsule is diverging,    -   occupant can request a divergence, however divergence force not        directly controlled by occupant.    -   Divergence forces balanced through CG and through center of        lift:

The magnetic gradient generated by the permanent magnet material 105 canbe shaped and configured to introduce a limited degree of freedom in thelateral direction as shown in FIG. 5.

The ETT-HTSM is capable of controlled freedom of movement in the lateraldirection with little lateral force applied as shown in the forcedistribution graph below the progression of permanent magnet 105 andsuperconductor 100 sections in FIG. 4. The dotted lines labeled “NSF” toindicate normal steering force level, and “ESF” for exceptional oremergency steering force level. This degree of freedom is dimensionallyexpanded in the diverge zone so the width of the degree of lateralfreedom (with low lateral force) becomes a little over double the normalwidth of the permanent magnet 105 strips in the normal (non-interchange)zone of the. This allows additional magnetic elements 105 to be insertedin the middle of the widened the permanent magnet 105 strips (one alongthe bottom and top of the evacuated tubes) such that a magnetic gradientis introduced in the center of the strip creating two parallel zoneswith reduced lateral freedom, and then the permanent magnet 105 stripscan bifurcate into two separate and parallel permanent magnet 105 stripsthat diverge into two separate tube routes. The converge zone isidentical, except the direction of flow is reversed.

The permanent magnet 105 strips are typically mounted 180 degrees apartat the top and bottom of the tube in straight sections (at 12:00 and6:00 positions in clock notation). In curves the permanent magnet 105strips are smoothly rotated at an angle in curves to correspond to anatural bank angle producing no (or only slight) lateral accelerationforce due to the curve-linear motion as shown in FIG. 6. The permanentmagnet strips can be of greater cross-section to provide more levitationforce as needed in vertical or horizontal curves that cause verticalaccelerations on the capsule. The vertical force generating power of thecomponents are not diminished in the converge/diverge zone.

ETT Interchange Elements:

Selectively polarized Magnetic force generators are oriented in or onthe capsule (or cryostats) to magnetically interact with ferromagnetic(and/or electromagnetic) material in corresponding areas in the tube tosupply ample steering force to cause the capsule to diverge at anydesired interchange. An interchange is a branch bifurcation.

Preferably, the active components in the vehicle cannot physically beactivated during a interchange operation—the interchange operation ispredetermined, either before the journey, or during an emergencysituation in route. And the active components in the vehicle are notdirectly controlled by the occupant—the occupants diverge input isfiltered by the control system. The lateral force generating magneticelements 190 in the vehicle can be permanent magnet or electricallyenergized with DC current.

Permanent magnets are inherently unstable as their strength diminisheswith time. This property of instability virtually guarantees safeoperation because the ETT switch design uses the instability toadvantage to create a bi-stable position−the vehicle is assured it willeither continue on the line, or diverge. Alternatively a simple DPDTbi-stable electric switch can selectively energize electromagnet switchelements 190 (or reverse the direction of current flow to reverse theorientation of the magnetic force field) such that attractive orrepulsive force can be selected to diverge or stay on the branch. Aninterrupter prevents the reorientation of switch elements while thevehicle is approaching and in the diverge zone.

For a converge, the capsule switch elements 190 are oriented to create aforce that biases the capsule to follow the side of the tube 200 that isopposite the tube 200 to merge with. In this way there is no abruptchange in force when entering the zone of increased lateral freedom. Ifthe switch 190 is improperly oriented by failure, there will be suddenlateral movement across the width of the permanent magnet 105 producingsome lateral jerk and light impact force, however the force will be muchless than the lateral magnetic restraining force the suspension elementsare capable of sustaining. This improper event is sensed by positionsensors, and/or accelerometers in the capsule 300 and indicates alikelihood of a component failure in the switch elements 190 in thecapsule, and the control system will flag the capsule for removal fromservice and repair at the next access portal.

Emergency Override:

In the rare event of a mechanical or electric switch failure in thecapsule magnetic polarity mechanism or circuit, electromagnets 194 inthe tube can be activated to overpower the magnets in the vehicle andforce a divergence of the capsule at a desired branch of the tube 200.

Another reason for the simplicity and safety of the ETT switch 190 isthat the tube 200 fully envelopes the capsule 300. In the extremelyimprobable event of an ETT failure, the vehicle will still continue bymomentum down one side or the other of any diverge zone in the vehicletrajectory (assuming the vehicle is intact).

Converge failure is strictly a timing issue, and converge timing may becontrolled by motor phase that is hardwired in, and by design will notfail unless two or more exceptionally improbable failures occur atexactly the same time.

Note that both levitation and steering forces are balanced to pass veryclose to both the lateral and vertical centers of gravity of thecapsule. The two points of magnetic suspension force are verticallyseparated by maximum distance allowed in the tube to generate a powerfulroll couple for high stability in the event that a load shifts (orpassengers jostle around) in the capsule.

It must be recognized that there are many embodiments that fall underthe scope of this invention. For instance if other ways are used toensure load stability (passenger and load restraints), then the capsulescan be supported only from above (primarily in attraction). Futurematerials may obviate the need for the heat sink cyrostat 110, all theother elements function the same with the same load paths, andoperation.

I claim:
 1. An evacuated tube transport system having removable magneticforce elements, comprising: (a) at least one evacuated tube ; (b) acapsule capable of traveling within the evacuated tube, the capsulehaving a top, a bottom, an inside and an outside, and a circularcross-section; (c) an upper and a lower cryostat respectively removeablymounted on the outside of the capsule; (d) at least a plurality ofsuperconductive magnetic elements enclosed by the upper and lowercryostats; (e) at least a pair of permanent magnetic elements mounted atthe top and bottom of the tube, the permanent magnets cooperate with thesuperconductor magnetic elements to levitate the capsule within theevacuated tube; (f) at least a pair of capsule based switchable divergeforce elements at least a pair of tube based diverge force elements toalign the capsule within the tube; and (g) the system includes aninterchange region with an airlock and a removable mounting element thatattaches the upper and lower cryostat to the capsule, the removablemounting element enables removal of the upper and lower cryostat fromthe capsule in the airlock.
 2. A system as set forth in claim 1, whereinthe cryostats are made of an electrically non-conductive material andconfigured in a cylindrical shape to house the superconductive magneticelements for use in linear induction motor/generator for capsuleacceleration/deceleration.
 3. A system as set forth in claim 1, whereineach cryostat contains superconductor elements made ofYttrium-Barium-Copper-Oxide (YBCO) crystals.
 4. A system as set forth inclaim 1, wherein each cryostat contains superconductor elements havingvapor deposited Yttrium-Barium-Copper-Oxide films.
 5. A system as setforth in claim 1, wherein the cryostat contains a cryogenic solid-liquidphase change material whereby the superconductor elements are cooled bythe cryogenic material.
 6. A system as set forth in claim 1, wherein aplurality of permanent magnetic elements are secured to the tube bynon-conductive structural permanent magnet mounts.
 7. A system as setforth in claim 6, wherein spacers separate the permanent magneticelements and the spacers are made from a dielectric material to reducemagnetic drag forces on the capsule.
 8. A system as set forth in claim7, wherein the permanent magnets are aligned with the cryostats tocooperate with the superconductive material to levitate the capsule inthe tube.
 9. A system as set forth in claim 8, wherein the permanentmagnets are coated with a reflective material to minimize heat transferbetween the capsule and the cryostats.
 10. A system as set forth inclaim 9, wherein a surface of the reflective material is etched toinhibit electrical currents through the reflective material and thusminimize magnetic drag forces.
 11. A system as set forth in claim 1further comprising, an insular mounting element, wherein the insularmounting element is made of an insular material selected from the groupconsisting of: syntactic foam, aerogel, polycarbonate foam, orcombinations thereof.
 12. An evacuated tube transport system havingremovable magnetic force elements, comprising: (a) at least oneevacuated tube ; (b) a capsule capable of traveling within the evacuatedtube, the capsule having a top, a bottom, an inside and an outside; (c)an upper and a lower cryostat respectively removeably mounted on theoutside of the capsule and having cryogenic material selected from thegroup consisting of propane and propane mixtures; (d) at least aplurality of superconductive magnetic elements enclosed by the upper andlower cryostats; (e) at least a pair of permanent magnetic elementsmounted at the top and bottom of the tube, the permanent magnetscooperate with the superconductor magnetic elements to levitate thecapsule within the evacuated tube; and (f) at least a pair of capsulebased switchable diverge force elements at least a pair of tube baseddiverge force elements to align the capsule within the tube.
 13. Anevacuated tube transport system having removable magnetic forceelements, comprising: (a) at least one evacuated tube ; (b) a capsulecapable of traveling within the evacuated tube, the capsule having atop, a bottom, an inside and an outside; (c) an upper and a lowercryostat respectively removeably mounted on the outside of the capsule;(d) at least a plurality of superconductive magnetic elements enclosedby the upper and lower cryostats; (e) at least a pair of permanentmagnetic elements mounted at the top and bottom of the tube, thepermanent magnets cooperate with the superconductor magnetic elements tolevitate the capsule within the evacuated tube; (f) at least a pair ofcapsule based switchable diverge force elements at least a pair of tubebased diverge force elements to align the capsule within the tube,wherein cryogenic material is placed in the cryostat with an expansionmitigation means for keeping the cryogenic material in contact with thesuperconductor elements and for allowing expansion and contraction ofthe cryogenic material during normal operation.
 14. A system as setforth in claim 13, wherein the expansion mitigation means is configuredas a flexible membrane separating a portion of the cryostat to allowchanges in cryogenic material volume without applying damaging cryostatdue to pressure changes.
 15. A system as set forth in claim 14, whereinthe cryostat is provided with reaction members as moving part of alinear electric motor having coil elements mounted on the tube.
 16. Asystem as set forth in claim 14, wherein the cryostat is provided withreaction members as moving part of a linear electric generator (LEG)having coil elements mounted on tube.